1. Field of the Invention
The present invention relates to a method of protecting an electricity storage device in a hybrid DC power supply system, which supplies electric power from two DC power supply devices to a load, e.g., a hybrid DC power supply system applied to a fuel cell vehicle, wherein electric power is supplied from a battery and a fuel cell to an inverter-driven motor.
2. Description of the Related Art
Heretofore, there has been proposed an electric vehicle in which a vehicle propelling motor (electric motor) is energized by a battery (see, Japanese Laid-Open Patent Publication No. 09-284902).
A fuse is connected to an output terminal of the battery. When an overcurrent flows from the battery, a fuse is blown immediately in order to prevent the overcurrent from flowing from the battery, thereby protecting the battery.
When the fuse is blown, the battery is unable to supply electric power until the fuse is replaced with a new one. As a result, in the meantime, the electric vehicle cannot be used.
It also is known in the art that an excessive charging current or discharging current should not flow through the battery, in order to prevent the battery from becoming unduly deteriorated.